Many automotive engines have an air pump which delivers air for injection into the engine exhaust system to support oxidation of hydrocarbons and carbon monoxide. In such a system, the air pump is engine driven, and the pressure of the air delivered by the pump increases with the speed of the engine. However, the pressure of the air injected into the exhaust system must be limited to a predetermined maximum, and automotive air injection systems generally include a pressure relief valve which allows the excess air delivered by the pump to be directed away from the exhaust system.
The pressure relief valve is often included in an air management valve assembly which controls air flow to the exhaust system in accordance with operating conditions. The various functions of the air management value assembly are tested at the manufacturing plant; prior to this invention, the pressure relief valve was not accessible for repair, and the entire air management valve assembly had to be scrapped if a test showed that the pressure relief valve was not performing in the required manner.